In general, the present invention is widely applicable to the production of materials for electronic device such as semiconductors or semiconductor devices, and liquid crystal devices. For the convenience of explanation, however, the background art relating to semiconductor devices as an example of the electronic devices, will be described here.
Substrates for semiconductors or electronic device materials such as silicon have been subjected to various kinds of treatments such as formation of an oxide film, film formation by CVD (chemical vapor deposition), etc., and etching. According to the recent requirement for forming microstructures and attaining further development in the performances in the field of semiconductor devices, the demand for an insulating film having a higher performance (for example, in view of leakage current) has been increased remarkably. This is because the leakage current of a certain degree can cause a severe problem in the recent devices which have attained finer structures, and/or higher performances, even when the leakage current of such a degree have actually caused substantially no problem in the conventional devices having a lower degree of integration. Particularly, in view of the development in the mobile or portable-type electronic devices in a so-called “ubiquitous” society of recent construction (i.e., information-oriented society wherein people can use a network service, anytime and anywhere, by means of electronic devices), it is necessary to develop a low-power consumption device, and therefore the reduction in the leakage current is an extremely important issue.
Typically, in a case where the formation of a finer structure in a high-performance silicon LSI is pursued, for example, for the purpose of developing a next-generation MOS-type transistor, there arises her performance a problem that the leakage current is increased and the resultant power consumption is also increased. Accordingly, in order to decrease the power consumption thereof while pursuing a higher performance, it is necessary to improve the transistor characteristic without increasing the gate leakage current in the MOS-type transistor.
In order to satisfy this requirement, various techniques (for example, the modification of a silicon oxide film and the use of a silicon oxynitride film SiON) have been proposed. Among these, one useful technique is the development of an insulating film using a high-k (high-dielectric constant) material. This is because the use of such a high-k material is expected to reduce the EOT (effective oxide thickness), which is an SiO2 capacity-equivalent film thickness.
However, when such an insulating film, which has been expected to provide a good property, is actually formed by CVD (chemical vapor deposition method) or the like, particularly in the case of the formation of an insulating film having a very high practical utility (for example, a relatively thin insulating film of about 12 A (angstrom)), a good interfacial property can be hardly obtained between the insulating film and the underlying electronic device substrate.
One promising method for solving such a problem may be to form a very thin (for example, 10 A or less) underlying film on a substrate, and to form an insulating film on the underlying film. However, it is very difficult to form such a thin underlying film directly on an electronic device substrate by using a conventional thermal oxidation or plasma oxidation technique (the thickness of a thin film can be hardly controlled by such a technique), while controlling the film-forming rate or in-plane uniformity.